1. Field of the Invention
The present invention relates to a fluorescent organism diagnosing apparatus for diagnosing, for example, early cancer through the fluorescent observation by an endoscope.
2. Description of Related Art
When an organism is irradiated with light of a certain wave length band, the organism fluoresces. A diagnosis based on this phenomenon is currently conducted using an endoscope.
The endoscope used for the fluorescent diagnosis is the same as a normal endoscope constructed to obtain an image of a subject portion by an objective optical system assembled into the tip of an insertion portion, and transmit the obtained image through an image guide fiber bundle extending inside the insertion portion to an ocular portion.
In a related fluorescent diagnosing apparatus, the observation image transmitted to the ocular portion is selectively guided by an optical-path switching member to one of image pickup faces of a normal image television camera for a normal image observation, and a fluorescent-image television camera (ultrasensitive camera) for a fluorescent image observation. The fluorescent-image television camera is provided with an image intensifier for amplifying the fluorescent image.
For the fluorescent observation, band-pass filter is inserted into an illumination optical path of the endoscope to illuminate the subject portion with light of a certain wave length band so that an organism tissue in the subject portion fluoresces. The band-pass filter considerably attenuates the light when the light passes therethrough, so that the light transmitted to the ocular portion is very weak.
If light of normal intensity enters the image intensifier due to the fact that the observation optical path is switched to the fluorescent-image television camera before the filter is inserted into the illumination optical path, a protection circuit is activated to turn off a power supply to the image intensifier since the light of normal intensity is too intensive and may damage circuits of the image intensifier and the fluorescent-image television camera. The activation of the protection circuit results in the interruption of the endoscopic observation, and it consumes much time and labor to return the fluorescent diagnosing apparatus to the original condition.
Accordingly, a first object of the present invention is to provide an arrangement for a fluorescent organism diagnosing apparatus, which can prevent light of such an intensity as to drive the protection circuit from entering a fluorescent-image TV camera, to thereby ensure a smooth fluorescent observation.
In the related fluorescent diagnosing apparatus, the optical-path switching member is arranged to have a reflector, such as a prism, and to be moved slidably in an optical axis direction of the normal image television camera in order to selectively guide the observation image to one of image pickup faces of the normal image television camera and the fluorescent-image television camera.
However, the optical-path switching member slides unsteadily and unsmoothly, and the reflector in the swithching optical member may be inclined with respect to the optical path. Those hinder the smooth switching operation and endoscopic observation.
Further, since the optical-path switching member is slidable in the optical axis direction of the normal-image television camera, a space allowing the optical-path switching member to move therein need to be secured along the optical path of the normal-image television camera. Consequently, the optical path length of an optical-path switch section in the apparatus is long, which leads to the increase in the entire size of the apparatus, the loss of the light transmission, and the deterioration of image quality.
Accordingly, a second object of the present invention is to provided an arrangement for a fluorescent diagnosing apparatus, which can smoothly switch an optical path extending from the ocular portion of the endoscope to one of a normal-image television camera and a fluorescent-image television camera without increasing the optical-path length.
In the related fluorescent diagnosing apparatus, a normal image forming lens is generally located between the optical-path switching member and the normal-image television camera, whereas a fluorescent image forming lens is generally located between the optical-path switching member and the fluorescent-image television camera.
Therefore, various optical adjustment, e.g., focusing and eccentricity adjustments, are required between the normal image forming lens and the normal-image television camera and between the fluorescent image forming lens and the fluorescent-image television camera. Mechanisms for enabling those adjustments make the apparatus complicated in construction and difficult to assemble.
Accordingly, a third object of the present invention is to provide a fluorescent organism diagnosing apparatus, which has a simple and easy-to-assemble mechanism for enabling the necessary optical adjustment of a normal-image television camera and a fluorescent-image television camera.